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Current Issues
Overweight and obesity in Australia
E-Brief: Online Only issued 5 October 2006
Mandy
Biggs Analysis and Policy
Social Policy Section
Introduction
Reports of an obesity epidemic appear with
increasing frequency and rising concern in Australia. Particular
attention is given to reports of the accelerating rate of obesity
among Australian children. Despite this high profile of obesity as
a public health issue, some aspects of the debate rest on limited
evidence and/or outdated data, including: out-dated national time
trend data on children and inadequate measures of obesity and
overweight.
This e-brief provides links to sources and an
overview of the current state of obesity and overweight in
Australia. Information on how overweight and obesity are measured
is presented, followed by a brief discussion on the limitations of
these measures. Prevalence data for obesity and overweight in
children and adults is then presented and limitations of this data
are discussed. The need for a national nutrition survey and recent
developments in this area are discussed, and finally some links to
information and sources are provided.
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How obesity is measured
Obesity is most commonly measured using the body
mass index (BMI). BMI is a weight-to-height ratio, and is
considered to be a reasonable reflection of body fat for most
people. BMI is calculated by dividing body weight in kilograms by
the square of height in metres (kg/m).
Among adults, a person with a BMI greater than
25kg/m is considered overweight, while a BMI greater than 30kg/m is
considered obese. The table below shows the BMI cut-off points
widely accepted for use among adults in Australia, and which relate
to points where the risks of adverse health outcomes rise
sharply.
Source: NHMRC
International BMI-for-age tables were developed for
children using the adult cut-off points as references. The
Department of Health and Ageing has published these
BMI-for-age-tables.
However, while recommending the use of BMI tables
the National Health and Medical Research Council (NHMRC) in its
Dietary
Guidelines for Children and Adolescents, notes some limitations
with the tables as they apply to children (see Part B of the
chapter Special Considerations ). First, the cut-off points chosen
to classify overweight and obesity in children are arbitrary,
without evidence of an association with adverse health outcomes
(unlike cut-off points for adults, which have been linked to
adverse health outcomes).
Second, because Australia does not currently have
growth reference charts derived from the local population, a
reference from another population is used; currently the US
National Center for Health Statistics (now the Centers for Disease
Control) growth
charts are used. However, these are based on data derived from
infants who were not exclusively breastfed (formula fed babies tend
to be heavier than breast fed babies).
Third, the BMI measure is not considered the most
accurate measure of abdominal obesity (more accurate measures are
magnetic resource imaging or dual energy X-ray absorptiometry).
Lastly, the NHMRC notes that BMI does not allow for ethnic
variations in weight and fat distribution.
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Prevalence - Children
Measuring obesity in children can be problematic
due to differences in developmental rates and maturation.
Further, recent national time trend data on the
prevalence of obesity in Australian children and adolescents are
not available. The most recent national survey data come from the
1985 Australian Health and Fitness Survey (AHFS) and the 1995
National Nutrition Survey (NNS). Drawing on data from these
surveys, which use the above BMI tables to define overweight and
obesity, the Australian Institute
of Health and Welfare (AIHW) reported the following prevalence
rates in a recent
brief:
- 15.3% of boys and 16.0% of girls (aged 7 15 years), were
overweight in 1995, compared to 9.3% of boys and 10.6% of girls in
1985
- 4.7% of boys and 5.5% of girls (aged 7 15 years) were obese in
1995, compared to 1.4% of boys and 1.2% of girls in 1985
- 21.5% of girls and 20% of boys were either overweight or obese
in 1995, and
- in the ten year period from 1985 to 1995 the prevalence of
obesity alone among 7 15 year-olds more than tripled.
See the figure below:
Source: AIHW
Detailed analysis of age group data undertaken by
the AIHW
in the recent brief, shows that the prevalence of overweight and
obesity varies considerably across sex and age levels:
- In 1995 boys aged 10 14 had the
highest levels of overweight (18.3%), while for girls those aged 2
4 had the highest levels (18.5%)
- the highest levels of obesity for
boys occurred among the 15 17 year old age group (6.1%), and for
girls among the 5 9 year old age group (7.1%)
- 15.3% of 2 17 year olds were
overweight and 4.6% obese, and
- overall, one in five or 19.9% of
Australian children aged 2 17 were overweight or obese in
1995.
See figure below:
Source: AIHW
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Other Australian data
Citing data from more recent regional and state
surveys of school students, the AIHW s
brief concludes that the rates of overweight and obesity among
young Australians are accelerating. This data includes:
- a 2000 survey of NSW primary school children aged 7 11, where
the prevalence of overweight was reported at 26.2% of boys surveyed
and 28.4% of girls, while the prevalence of obesity was reported at
9.9% of boys and 7.1% of girls (all increases from the levels
reported in the NNS in 1995)
- the 2003 Sentinel Site for Obesity Prevention in Victoria study
which reported that 26.7% of 7 11 year olds surveyed were classed
as overweight, while 7.9% were classed as obese
- analysis of data collected in state surveys between 1967 and
1997 shows that from the mid-1980s to the mid-1990s the prevalence
of obesity tripled and that of overweight doubled among 7 15 year
olds, compared with a much smaller rate of increase over the
preceding 16 years.
However, it is unclear if this accelerated trend is
continuing. Recently released data from the NSW
Schools Physical Activity and Nutrition Survey in 2004 found
that of the 5 16 year olds surveyed, 25% of boys and 23.3% of girls
were either overweight or obese (up from the 1995 data but similar
to results reported in 2000 and 2003).
Other data indicates that obesity may be developing
at a much younger age. According to recent research from South
Australia cited in the AIHW
brief, the percentage of obese preschoolers (children aged four
years) in South Australia rose from 3.5% for girls and 3.2% for
boys in 1995 to 5.8% for girls and 4.1% for boys in 2002.
As can be seen from the table below, international
comparisons of obesity are especially problematic for children,
because of the different age ranges that are measured and
differences in the years in which surveys are conducted.
Source: AIHW
Despite the data presented from these surveys and
studies, the absence of a recent national nutrition survey means
that accurate and reliable nutritional and energy intake data on
Australian children is missing.
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Prevalence - Adults
The most recent national data on overweight and
obesity for adults (aged 18 75) is based on self-reported BMI data
from the 2004 05
National Health Survey (NHS). It should be noted that
self-reported data is considered less reliable than measured data
(because people tend to overestimate their height and underestimate
their weight). The survey showed that:
- overall 32.6% of adults were
reported as overweight in 2004 05
- 40.5% of males and 24.9% of females
were overweight
- overall 16.4% of adults were
reported as obese in 2004 05
- 17.8% of males and 15.1% of females
were obese.
The
NHS showed higher rates of overweight or obesity in older age
groups. Those in the 55 64 age group had the highest combined rates
of overweight and obesity; 72% of males and 58% of females.
The prevalence of overweight and obesity increased
markedly between 1995 and 2004 05, according to historical data
presented in the 2004-05
NHS. Levels of overweight increased from 29.5% reported in the
1995 NHS to 32.6% in 2004-05. At the more severe end of the
spectrum, the prevalence of obesity among Australian adults was
11.1% in 1995, rising to 16.4% 2004 05.
In Australia
s Health 2006, the AIHW reports a similar prevalence of
overweight and obesity in Australian adults across the states and
territories, according to analysis it undertook on figures derived
from the NHS. Obesity rates ranged from 17.0% in Victoria to 19.6%
in South Australia, and overweight rates from 34.2% in Queensland
to 36.3% in Victoria.
Measured height and weight data were also collected
nationally in the 2000 AusDiab
study, and in the 2005 follow up study. Analysis of AusDiab
data by the AIHW reported in Australia
s Health 2006, found that of those surveyed 19% of males
and 22% of females aged 25 years or over were obese and an
additional 48% of males and 30% of females were overweight in 1999
2000. In this sample, males were more likely than females to be
overweight or obese (67% versus 52%). The prevalence of obesity was
found to be highest among those aged 55 64 (29%), with the lowest
rates being among those aged 25 34 (15%) or 75 years and over
(14%). Prevalence patterns for all overweight people were similar,
with the prevalence increasing with age to 65 74 years, and
declining thereafter.
The 2005
AusDiab follow up study by Barr et al, found that over the
period of follow up there was an increase in average weight, BMI
and waist circumference in both males and females. On average those
aged under 65 at baseline showed a weight increase of 1.8 kg (those
aged 65 74 showed a slight decline in weight, but an increase in
BMI).
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International comparisons
As noted above international comparisons on obesity
can be problematic because data is not always directly comparable.
However, recent data indicates that the prevalence of overweight
adult Australians is similar to that in the US, Canada and the UK;
prevalence of obesity is lower than the US, but similar to both the
UK and Canada. See figure below:
Source: AIHW
In its recent survey of chronic disease risk
factors, the
World Health Organisation estimated that 75.7% of males and
66.5% of females in Australia will be overweight by 2010, and 28.4%
of adult males and 29.1% of adult females will be obese, if current
trends continue.
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A national survey
Despite the range and type of overweight and
obesity data available (as is shown in the data presented here), it
has been
noted by public health and nutrition experts that Australia has
lacked consistent national data on nutrition and energy intake. In
the last 50 years Australia has conducted only three national
surveys of diet: a survey of adults in 1983, of children in 1985,
and the NNS in 1995, which surveyed both adults and children. Each
of these surveys was conducted by a different agency using
different survey techniques, making ongoing analysis of nutrition
and energy intake over time difficult to undertake, and limiting
our ability to understand trends in food and nutrient
consumption.
In 2005 the federal government announced funding of
$3m for a joint Australian government/food industry initiative
called
Measuring Australia s eating habits and physical activity,
to collect national data on nutrition and physical activity. The
project is a joint initiative of the Department of Health and
Ageing, the Department of Agriculture, Fisheries and Forestry and
the Australian Food and Grocery Council, which are each
contributing $1m to the project.
In April 2006 the AMA criticised
the project, describing it as underfunded and calling for a
government funded national nutrition survey. Also in April the
report
A national food and nutrition monitoring surveillance system
commissioned by the Department of Health and Ageing was released,
which noted the ongoing and overwhelming support from stakeholders
for a national nutrition surveillance system. The report estimated
that the cost of establishing and maintaining an annual nutrition
survey would be $1.2 million annually.
Further
details of the joint initiative were announced in July 2006,
including that the national nutrition and physical activity survey
will be undertaken by the CSIRO and the University of South
Australia for completion before 2007. Furthermore, the Department
had committed annual funding of $1m a year for a national ongoing
program to collect data on food, nutrition, physical activity
habits, and physical measurements of all population groups.
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Links to sources
Australian Institute of Health and Welfare
A
growing problem. Trends and patterns in overweight and obesity
among adults in Australia, 1980 to 2001.
Are
all Australians gaining weight? Differentials in overweight and
obesity among adults, 1989-90 to 2001.
A
rising epidemic: obesity in Australian children and
adolescents
Obesity
trends in older Australians.
Health,
wellbeing and body weight: characteristics of overweight and
obesity in Australia, 2001 and Physical
activity, diet and body weight: results from the 2001 National
Health Survey.
The
health and welfare of Australia s Aboriginal and Torres Strait
Islander people, chapter 8, Health risk factors
See also Australia
s health 2006 chapter 3 section on biomedical determinants
of health.
Other sources/information
T. Abbott,
National children s survey to help tackle obesity Media Release
19 July 2006.
ABS
National Health Survey 2004-05: Summary of results
ELM Barr, et al., AusDiab 2005:
the Australian diabetes, obesity and lifestyle study
International Diabetes Institute, Melbourne, 2006. (Executive
summary only available online)
Booth, M, Okely AD, Denney-Wilson,
E, Hardy L, Yang, B, Dobbins T, NSW
Schools Physical Activity and Nutrition Survey (SPANS) 2004 Summary
Report. NSW Health, 2006.
Centers for Disease Control National
Center for Health Statistics (US) 2000 CDC Growth charts: United
States
Department of Health and Ageing
Healthy Weight website.
D Dunstan, et al, The Australian
Diabetes, Obesity and Lifestyle report (AusDiab) 2000
International Diabetes Institute, 2001.
International Obesity Taskforce
Obesity in children and young people: a crisis in public health:
report to the World Health organization Obesity
Reviews vol 5 (supp 1) May 2004
P McGauran, and C Pyne,
New $3m project to help tackle childhood obesity Press release,
13 September 2005
National Health and Medical Research
Council Dietary
guidelines for children and adolescents in Australia
NHMRC, 2003.
National Health and Medical Research
Council Dietary
guidelines for Australian adults NHMRC, 2003.
Nexus Management Consulting.
A national food and nutrition monitoring and surveillance system: a
framework and a business case: Final report April 2006.
Department of Human Services,
Victoria
Information about the growth charts: key questions (CDC growth
charts)
KL Webb, IH Rutishauser, GC Marks, G
Masters, SR Leeder,
Nutrition surveys or surveillance: one night stands or a long term
commitment? Medical Journal of Australia vol 185 (5)
pp 248-249.
WHO
The SuRF Report 2: Surveillance of chronic disease Risk
Factors WHO, 2005.
For copyright reasons
some linked items are only available to members of
Parliament.
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